The present invention relates to clarifiers of a type wherein flow passages formed between a plurality of inclined plates and more particularly to such clarifiers wherein a liquid to be clarified flows generally horizontally through the flow passages.
Various types of clarifiers are being developed for use in place of large settling basins, tanks or the like where liquid is held over prolonged periods of time until clarification naturally occurs because of normal sedimentation rates and phase separation phenomenon. Inclined plate clarifiers are of increasing interest particularly in industrial and municipal water treatment facilities because of increasingly rigid requirements for effluent quality. In addition, settling basins and the like depend upon relatively long holding periods in order to accomplish separation and accordingly require excessive amounts of space. Inclined plate clarifiers in general have been found a very desirable means for overcoming these problems.
Inclined plate clarifiers are commonly characterized by aligned flow passages formed by a plurality of inclined plates. The use of such inclined plate clarifiers has been found to be a most effective means for increasing the settling area per unit volume while at the same time reducing size and cost as well as increasing the quality or clarity of effluent from the water treatment facility.
Inclined plate clarifiers may generally be divided into classes adapted for vertical flow or "cross-flow". Vertical flow clarifiers may be adapted for operation in either an "up-flow" or "down-flow" mode with relatively heavy and/or light phase material being removed.
The present invention particularly contemplates a cross-flow clarifier in which liquid to be clarified flows generally horizontally through flow passages formed by the inclined plates. Thus, inlet and outlet chambers for the liquid are in communication with the lateral ends of the inclined plates rather than with the upper and lower ends of the plates as in a vertical flow clarifier.
A cross-flow clarifier of this type may therefore require somewhat greater floor space or area than a vertical flow clarifier. However, the overall volume is approximately equal for the two types of clarifiers since it is not necessary in a cross-flow clarifier to provide means at the upper and lower ends of the inclined plates for entry and exit of the liquid to be clarified. In addition, since the liquid to be clarified flows horizontally, cross-flow clarifiers may be easily adapted to facilitate the removal of separate phases at both the tops and bottoms of inclined plates.
Otherwise, cross-flow clarifiers encounter many of the same problems as the vertical flow clarifiers. For example, it is commonly necessary that the clarifier be uniquely tailored to a particular application where the clarifier is being used. Accordingly, the cost of designing and installing clarifiers for each application tends to be quite substantial. For the same reason, operating procedures for such clarifiers have tended to vary widely in different applications and under different operating conditions.
In adapting the clarifier for operation under such widely varying conditions, it is necessary to assure that the clarifier can be readily assembled during its installation or disassembled and reassembled for example during cleaning.
In addition, it is a common problem in such clarifiers to regulate fluid flow both into and out of the flow passages between the inclined plates while maintaining uniform distribution of the fluid between the passages formed by the various plates.
Particularly with a cross-flow clarifier of the type contemplated by the present invention, it is a problem to maintain laminar horizontal flow of the liquid to be clarified through the flow passages between the inclined plates while allowing a heavier phase, usually suspended solids, to pass downwardly toward a settling chamber beneath the inclined plates. At the same time, a lighter phase such as oil, for example, may pass upwardly toward the top of the inclined plate for collection in a suitable separation chamber.
Various clarifiers in the prior art have demonstrated an ability to resolve or satisfy one or more of these problems. However, a need has been found to remain for a cross-flow clarifier which is adaptable to a variety of operating conditions and which may be employed to produce a relatively high quality effluent.